Composite air entraining agent for plateau anti-freezing concrete and preparation method of composite air entraining agent

Abstract

The invention provides a composite air entraining agent for plateau anti-freezing concrete and a preparation method of the composite air entraining agent, and belongs to the technical field of building materials. The composite air entraining agent is prepared from the following raw materials: a sulfonate gemini surfactant, dodecyl sulfobetaine, fatty alcohol-polyoxyethylene ether, a thickening agent, modified nano silicon dioxide, a foam stabilizer and deionized water. The sulfonate gemini surfactant, the dodecyl sulfobetaine and the fatty alcohol-polyoxyethylene ether are used as air entraining components of the composite air entraining agent, the thickening agent, the modified nano silicon dioxide and the foam stabilizer are used as air stabilizing components of the composite air entraining agent, and the proportion of all the components is reasonably optimized; the prepared air entraining agent has a good air entraining effect, good foaming ability and foam stability, and has a wide application prospect in a plateau low-pressure environment.

Description

Technical Field

[0001] The present invention relates to the technical field of building materials, and particularly relates to a composite air-entraining agent for high-altitude frost-resistant concrete and a preparation method thereof. Background Art

[0002] In recent years, the infrastructure construction in the plateau areas of our country has developed rapidly. As one of the most widely used building materials, concrete has been used on a large scale in the plateau areas. The plateau areas have a high altitude, thin air, low air pressure, low average annual temperature, large daily and annual temperature differences, and the number of annual freeze-thaw cycles reaches more than 300 times. The freeze-thaw cycle caused by the alternation of moisture and positive and negative temperatures in the environment leads to the freeze-thaw damage of concrete. Therefore, freeze-thaw damage has become the primary problem of the durability of concrete in the plateau areas, and adding an air-entraining agent to concrete has become one of the key measures to solve the frost resistance of concrete.

[0003] The air-entraining agent was first applied by American scholars during construction, and the "Vinsol" resin air-entraining agent was successfully prepared in 1937. Since then, the concrete air-entraining agent has been gradually promoted and applied. In recent years, a series of studies on air-entraining agents have been carried out in China, and many different types of air-entraining agents have been obtained. Currently, the commonly used air-entraining agents include: (1) Rosin-based: It has the characteristics of simple preparation, low price, good air-entraining property, but poor water solubility; (2) Alkylbenzene sulfonates: It has the characteristics of good foaming property, large bubbles, and poor foam stability; (3) Saponins: It has the characteristics of good water solubility, easy deliquescence, good bubble structure, but poor foaming property; (4) Fatty acids and their salts: It has the characteristics of poor foaming property and small bubbles. The above several types of air-entraining agents have their own advantages and disadvantages, but they have poor adaptability in high-altitude concrete. Due to the low air pressure, problems such as high air-entraining agent dosage, poor foaming property, easy bubble breakage, and poor foam stability occur, and the foaming property and foam stability are poor.

[0004] Based on this, on the basis of optimizing the existing air-entraining agent formula, the present invention provides a composite air-entraining agent for high-altitude frost-resistant concrete with good air-entraining property and foam stability. Summary of the Invention

[0005] To solve the deficiencies of the existing technology, the main purpose of the present invention is to provide a composite air-entraining agent for frost-resistant concrete and a preparation method thereof. The composite air-entraining agent of the present invention uses sulfonate gemini surfactant, dodecyl sulfobetaine, and fatty alcohol polyoxyethylene ether as the air-entraining components of the composite air-entraining agent, and uses thickener, modified nano-silica, and foam stabilizer as the air-stabilizing components of the composite air-entraining agent, so that the prepared composite air-entraining agent has a good air-entraining effect, good foaming ability and foam stability, and can significantly improve the frost resistance and durability of concrete in the plateau areas.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is:

[0007] A composite air-entraining agent for plateau anti-freezing concrete, comprising the following raw materials in parts by weight: 30-40 parts of sulfonate gemini surfactant, 20-30 parts of dodecyl sulfobetaine, 5-15 parts of fatty alcohol polyoxyethylene ether, 10-20 parts of thickener, 8-12 parts of modified nano-silica, 6-14 parts of foam stabilizer, and 200-300 parts of deionized water.

[0008] Preferably, the structural formula of the sulfonate gemini surfactant is:

[0009]

[0010] The above sulfonate gemini surfactant uses 1,2-diepoxydodecane as a raw material, obtains a ring-opening compound under the action of sodium hydride and benzyl alcohol, then generates a double-chain compound under the action of sodium hydride and 2-bromododecanoic acid, and is prepared by reduction with lithium aluminum hydride and palladium-carbon, esterification, and then hydrolysis.

[0011] The synthesis route of the above sulfonate gemini surfactant is as follows:

[0012]

[0013] In the above technical solution, the sulfonate gemini surfactant has two hydrophobic tails, two hydrophilic heads, and a linking group, and has high surface activity; it can effectively reduce the surface tension of water, promote the uniform distribution of bubbles in the concrete mixture, form stable micro-bubbles, and these bubbles improve the freeze-thaw resistance of the concrete, improve workability and pumpability, and reduce shrinkage cracks caused by water evaporation; dodecyl sulfobetaine, as an amphoteric surfactant, can enhance the stability of the foam, prevent the bubbles from merging or bursting, so as to maintain the required air content in the concrete; fatty alcohol polyoxyethylene ether, as a non-ionic surfactant, further reduces the tension at the gas-liquid interface and helps to generate finer and more stable bubbles. The synergistic work of the above surfactants optimizes the air-entraining effect of the concrete, improves the air-entraining efficiency and frost resistance of the concrete.

[0014] Preferably, the thickener includes at least one of hydroxyethyl cellulose, hydroxypropyl methyl cellulose, polyacrylamide, and sodium polyacrylate. When the air-entraining agent is incorporated with the thickener, it can increase the viscosity of the concrete mixture, reduce the fusion, overflow, and rupture between bubbles, ensure sufficient air content in the concrete, and improve the freeze-thaw resistance of the concrete; the thickener also helps to retain the moisture inside the concrete, prevent the rapid loss of moisture, reduce the formation of surface cracks, and improve the durability of the concrete.

[0015] Preferably, the foam stabilizer includes at least one of modified silicone resin polyether emulsion, fluorocarbon surfactant, and coconut oil diethanolamide. As a foam stabilizer, the modified silicone resin polyether emulsion changes the internal molecular arrangement order, making the surfactant bubbles arranged tightly and neatly between bubbles, thus forming a dense inner layer film, enhancing the compressive capacity of the foam. At the same time, it can control the structural stability of the bubble liquid film, making the surfactant molecules distributed orderly on the liquid film of the bubbles, endowing the foam with good elasticity and self-healing ability, so as to achieve an ideal foam stabilizing effect. The fluorocarbon surfactant can significantly reduce the surface tension of the liquid-gas interface, making the bubbles easier to form and more stable. It can also promote the uniform distribution of the bubbles, forming a fine and stable bubble network. Moreover, the introduced fine bubbles can form a buffer layer inside the concrete, reducing the damage of the low-temperature environment to the concrete structure, thereby improving its freeze-thaw resistance. Coconut oil diethanolamide has excellent wettability and dispersibility, improving the workability of the concrete and making the concrete easier to construct. Adding a foam stabilizer to the air-entraining agent significantly improves the comprehensive performance of the concrete and ensures the durability of the concrete in the plateau low-pressure environment.

[0016] More preferably, the fluorocarbon surfactant is an ammonium oxide type fluorocarbon surfactant, selected from perfluoroalkyl ether ammonium oxide type cationic fluorocarbon surfactants.

[0017] Preferably, the preparation method of the modified nano-silica includes the following steps:

[0018] (1) Prepare a mixed solution by placing a vinyl silane coupling agent in a mixed solvent of ethanol and water;

[0019] (2) Disperse the nano-silica in the mixed solution, stir and react, then filter, wash, and dry to obtain the modified nano-silica.

[0020] Preferably, in the step (1), the vinyl silane coupling agent includes at least one of γ-methacryloxypropyltrimethoxysilane, vinyltris(β-methoxyethoxy)silane, triacetoxyvinylsilane, and vinyltrimethoxysilane.

[0021] Preferably, in the step (1), the concentration of the vinyl silane coupling agent in the mixed solution is 5-8 wt%.

[0022] Preferably, in the step (2), the stirring time is 4-6 h; the drying temperature is 90-110 °C.

[0023] In the above solution, the modified nano-silica has high surface activity and can form a protective film at the gas-liquid interface to prevent bubble fusion and rupture, making the bubbles more stable and durable. These bubbles act as stress buffers to reduce the internal stress caused by temperature changes, thereby enhancing the frost resistance of concrete. Moreover, the modified nano-silica can also fill the pores of concrete, improve the density of concrete, reduce the water penetration path, improve the microscopic structure of concrete, and effectively improve the comprehensive mechanical properties of early-age concrete.

[0024] The present invention also provides a preparation method of the above composite air-entraining agent for high-altitude frost-resistant concrete, which includes the following steps:

[0025] S1. Add sulfonate gemini surfactant, dodecyl sulfobetaine, and fatty alcohol polyoxyethylene ether into deionized water. After stirring evenly, a mixed solution I is obtained.

[0026] S2. Add a thickening agent to the mixed solution I. After stirring evenly, slowly add modified nano-silica and stir evenly to obtain a mixed solution II.

[0027] S3. Add a foam stabilizer to the mixed solution II and stir evenly to obtain the composite air-entraining agent.

[0028] The present invention also provides the application of the composite air-entraining agent in the preparation of frost-resistant concrete.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. The present invention uses sulfonate gemini surfactant, amphoteric surfactant, and non-ionic surfactant as the air-entraining components of the composite air-entraining agent. The three are used in combination, making the composite air-entraining agent have good low-temperature stability. The thickening agent, modified nano-silica, and foam stabilizer are used as the gas-stabilizing components of the composite air-entraining agent to stabilize the bubbles and prevent the bubbles from bursting, ensuring that the concrete has a certain air content.

[0031] 2. The present invention adjusts the ratio of the composite air-entraining agent, so that the prepared air-entraining agent has good foaming property and foam stability. The air-entraining agent of the present invention can not only improve the workability of concrete, making the construction more convenient, but also increase the air content of concrete, further enhancing the frost resistance and durability of concrete. Specific embodiments

[0032] The modified nano-silica of the present invention is prepared by the following method, specifically:

[0033] (1) Add 6 g of vinyltriethoxysilane into a mixed solution of 100 ml of ethanol and water with a mass ratio of 1:1, and stir at 1000 rmp for 30 min to prepare a mixed solution.

[0034] (2) Add 30 g of nano-silica to the above mixed solution, stir at 70 °C for 4 - 5 h. After the reaction is completed, filter, wash the filter cake with a mixed solution of ethanol and water, and dry the filter cake at 100 °C for 4 h to obtain modified nano-silica.

[0035] Example 1:

[0036] A composite air-entraining agent for high-altitude anti-freezing concrete, comprising the following raw materials in parts by weight: 30 parts of sulfonate gemini surfactant, 20 parts of dodecyl sulfobetaine, 5 parts of fatty alcohol polyoxyethylene ether, 10 parts of hydroxymethyl cellulose, 8 parts of modified nano-silica, 4 parts of modified silicone resin polyether emulsion, 1 part of ammonium oxide type fluorocarbon surfactant, 1 part of coconut oil diethanolamide, and 200 parts of deionized water.

[0037] The preparation method of the composite air-entraining agent for high-altitude anti-freezing concrete comprises the following steps:

[0038] S1. Add the sulfonate gemini surfactant, dodecyl sulfobetaine, and fatty alcohol polyoxyethylene ether to deionized water, and stir evenly at 1000 rmp to obtain a mixed solution I;

[0039] S2. Add hydroxymethyl cellulose to the mixed solution I, stir evenly, and slowly add modified nano-silica, and stir evenly at 500 rmp to obtain a mixed solution II;

[0040] S3. Add the modified silicone resin polyether emulsion, coconut oil diethanolamide, and ammonium oxide type fluorocarbon surfactant to the mixed solution II, and stir evenly to obtain the composite air-entraining agent.

[0041] Example 2:

[0042] A composite air-entraining agent for high-altitude anti-freezing concrete, comprising the following raw materials in parts by weight: 40 parts of sulfonate gemini surfactant, 30 parts of dodecyl sulfobetaine, 15 parts of fatty alcohol polyoxyethylene ether, 20 parts of hydroxymethyl cellulose, 12 parts of modified nano-silica, 10 parts of modified silicone resin polyether emulsion, 2 parts of ammonium oxide type fluorocarbon surfactant, 2 parts of coconut oil diethanolamide, and 300 parts of deionized water.

[0043] The preparation method of the composite air-entraining agent for high-altitude anti-freezing concrete comprises the following steps:

[0044] S1. Add the sulfonate gemini surfactant, dodecyl sulfobetaine, and fatty alcohol polyoxyethylene ether to deionized water, and stir evenly at 1000 rmp to obtain a mixed solution I;

[0045] S2. Add hydroxyethyl cellulose to the mixture I, stir evenly, then slowly add modified nano-silica dioxide, and stir evenly at 500 rmp to obtain mixture II;

[0046] S3. Add modified silicone resin polyether emulsion, coconut oil diethanolamide, and ammonium oxide type fluorocarbon surfactant to the mixture II, stir evenly, and then the composite air-entraining agent is obtained.

[0047] Example 3:

[0048] A composite air-entraining agent for high-altitude frost-resistant concrete, comprising the following raw materials in parts by weight: 35 parts of sulfonate gemini surfactant, 25 parts of dodecyl sulfobetaine, 10 parts of fatty alcohol polyoxyethylene ether, 15 parts of hydroxyethyl cellulose, 10 parts of modified nano-silica dioxide, 7 parts of modified silicone resin polyether emulsion, 2 parts of ammonium oxide type fluorocarbon surfactant, 2 parts of coconut oil diethanolamide, and 250 parts of deionized water.

[0049] The preparation method of the composite air-entraining agent for high-altitude frost-resistant concrete comprises the following steps:

[0050] S1. Add sulfonate gemini surfactant, dodecyl sulfobetaine, and fatty alcohol polyoxyethylene ether to deionized water, stir evenly at 1000 rmp, and then mixture I is obtained;

[0051] S2. Add hydroxyethyl cellulose to the mixture I, stir evenly, then slowly add modified nano-silica dioxide, and stir evenly at 500 rmp to obtain mixture II;

[0052] S3. Add modified silicone resin polyether emulsion, coconut oil diethanolamide, and ammonium oxide type fluorocarbon surfactant to the mixture II, stir evenly, and then the composite air-entraining agent is obtained.

[0053] Comparative Example 1:

[0054] The difference from Example 3 is that dodecyl betaine is not added.

[0055] Comparative Example 2:

[0056] The difference from Example 3 is that unmodified nano-silica dioxide is added.

[0057] Comparative Example 3:

[0058] The difference from Example 3 is that ammonium oxide type fluorocarbon surfactant is not added.

[0059] Comparative Example 4:

[0060] Sodium dodecyl sulfate is used as the air-entraining agent.

[0061] Dilute the composite air-entraining agents prepared in the above Examples 1-3 and Comparative Examples 1-4 to a concentration of 1 wt%, and conduct performance tests with reference to the relevant provisions of the national standard GB8076-2008 "Concrete Admixtures". The performance test results of each example and comparative example are shown in Table 1.

[0062] Table 1

[0063]

[0064]

[0065] It can be seen from Table 1 that compared with Comparative Examples 1-4, Examples 1-3 of the present invention incorporate less composite air-entraining agent, making the initial air content in each type of concrete close. This shows that the composite air-entraining agent of the present invention has a good air-entraining effect. When using the composite air-entraining agents prepared in Examples 1-3 of the present invention, the change in the air content of the concrete is relatively small, and the 28-day compressive strength ratio and relative durability index are both superior to those of the comparative examples. This shows that the concrete composite air-entraining agent prepared by the present invention has excellent air-entraining and air-stabilizing effects and has broad application prospects in the plateau low-air-pressure environment.

[0066] The above embodiments are only the preferred technical solutions of the present invention and should not be regarded as limitations on the present invention. The protection scope of the present invention should be the technical solutions recorded in the claims, including equivalent replacement solutions of the technical features in the technical solutions recorded in the claims. That is, equivalent replacement improvements within this scope are also within the protection scope of the present invention.

Claims

1. A composite air entraining agent for plateau frost-resistant concrete, characterized in that: The invention comprises the following raw materials in parts by weight: 30-40 parts of sulfonate gemini surfactant, 20-30 parts of dodecyl sulfobetaine, 5-15 parts of fatty alcohol polyoxyethylene ether, 8-15 parts of thickener, 8-12 parts of modified nano silicon dioxide, 5-12 parts of foam stabilizer and 200-300 parts of deionized water.

2. The composite air entraining agent for plateau frost-resistant concrete according to claim 1, characterized in that: The sulfonate gemini surfactant structural formula is:

3. The composite air entraining agent for plateau frost-resistant concrete according to claim 1, characterized in that: The thickener includes at least one of hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose, polyacrylamide and sodium polyacrylate.

4. The composite air entraining agent for plateau frost-resistant concrete according to claim 1, characterized in that: The foam stabilizer comprises at least one of a modified silicone resin polyether emulsion, an ammonium oxide type fluorocarbon surfactant, and coconut oil diethanolamide.

5. The composite air entraining agent for plateau frost-resistant concrete according to claim 1, characterized in that: The preparation method of the modified nano silicon dioxide comprises the following steps: (1) dissolving a vinyl silane coupling agent in a mixed solvent of ethanol and water to obtain a mixed solution; (2) Dispersing nano-silicon dioxide in the mixed solution, stirring for reaction, filtering, washing and drying to obtain modified nano-silicon dioxide.

6. The composite air entraining agent for plateau frost-resistant concrete according to claim 5, characterized in that: In the step (1), the vinyl silane coupling agent includes at least one of γ-methacryloxypropyltrimethoxysilane, vinyl tri(β-methoxyethoxy)silane, triacetoxyvinylsilane and vinyl trimethoxysilane.

7. The composite air entraining agent for plateau frost-resistant concrete according to claim 5, characterized in that: In the step (1), the concentration of the vinyl silane coupling agent in the mixed solution is 5-8 wt %.

8. The composite air entraining agent for plateau frost-resistant concrete according to claim 5, characterized in that: In the step (2), the stirring time is 4-6 hours; and the drying temperature is 90-110°C.

9. The method for preparing the composite air entraining agent for plateau frost-resistant concrete according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1, dissolving sulfonate gemini surfactant, dodecyl sulfobetaine and fatty alcohol polyoxyethylene ether in deionized water, stirring evenly to obtain a mixed solution I; S2, adding a thickener to the mixed solution I, stirring evenly, slowly adding modified nano-silica, stirring evenly, to obtain a mixed solution II; S3. Add a foam stabilizer to the mixed liquid II and stir evenly to obtain a composite air entraining agent.

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